This invention relates to compression release engine braking methods and apparatus for use with turbocharged internal combustion engines having an intercooler between the turbocharger and the intake manifold.
Compression release engine brakes are well known as shown, for example, by Cummins U.S. Pat. No. 3,220,392, which is hereby incorporated by reference herein. Such brakes typically operate by opening the exhaust valves in the associated internal combustion engine near top dead center of the compression strokes of the engine pistons when engine braking is desired. This allows the gas compressed by the engine during its compression strokes to escape to the exhaust system of the engine, thereby preventing the engine from recovering the work of compression during the subsequent expansion strokes of the engine pistons. In effect, the compression release engine brake converts the engine from a power source to a power-sinking gas compressor during engine braking. (The fuel supply to the engine is of course cut off during such braking.) Compression release engine braking is desirable to save wear on the wheel brakes of a vehicle powered by the engine, as well as to increase the safety of operation of the vehicle.
As is well known, many engines are equipped with turbochargers which use the exhaust gases of the engine to spin a turbine. The turbocharger turbine spins a compressor which increases the pressure of the air supplied to the intake manifold of the engine. To prevent the compressed air from arriving at the intake manifold with an undesirably high temperature, an intercooler is often provided between the turbocharger compressor and the intake manifold. The intercooler typically provides a heat exchange between the air compressed by the turbocharger and ambient air to lower the temperature of the compressed air supplied to the intake manifold. Turbochargers and intercoolers allow engines of a given displacement to produce more power with an appropriate increase in injected fuel.
There is a constant demand for more effective compression release engine brakes, i.e., brakes which enable a given engine to produce more braking horsepower. For example, as the power mode power available from an engine increases, it is desirable, if possible, to commensurately increase the braking horsepower available from the engine during operation of an associated compression release engine brake. This is so because a more powerful engine is likely to be used to move heavier loads or to move loads at higher speeds, thereby producing a need for increased engine braking power.
In view of the foregoing, it is an object of this invention to improve the engine braking effectiveness of internal combustion engines equipped with compression release engine brakes, turbochargers, and intercoolers.